Incandescent cathode



Patented Apr. 5, 1932 STATS er Fries.

POPKO REINDER DIJKSTERHUIS, F EINIDIIOVEN, NETHERLANDS, ASSIGNOR, BYMESN E ASSIGNMENTS, TO RADIO CORPORA'EXON OF AMERICA, OFINEW YORK, N.Y.,

A CORPORATION INCANDEEZCENT CATHODE Application filed March 30, 1925,Serial No.

This invention relates to incandescent cathodes for. electric dischargetubes, more particularly to incandescent cathodes adapted to emit acomparatively great flux of electrons.

Such incandescent cathodes are used, for ex ample, in transmission tubesfor large outputs provided with three or more electrodes and destinedfor wireless telegraphy and the like or in rectifiers for large outputs.

The invention has in particular for its object to improve the manner inwhich the incandescent cathodes in discharge tubes are supported.

It is known to compose an electric incandescent body of two or moreparallel connected filament portions and to connect points of them withsubstantially the same potential by conductive members.

Where hereinafter the term filament is used, it has to be understood tomean the whole filament pertaining to the incandescent cathode. Thisfilament may consist of two or more portions which are separated fromeach other. The term incandescent cathode has to be understood to meanthe complex of the filament with the members that support it.

The invention has reference to an incandescent cathode comprisingparallel connected filament portions, which are supported by two or moremetal carriers serving at the same time to supply the current and it consists in that between the carriers serving to supply the current arearranged one or more other metal carriers which are connected tointerjacent equipotential points of the parallel filament portions.

According to the invention the filament may be wound on a number ofmetal supports, at lease two of which serve to supply the current.

Further characteristics of the invention will appear from which follows:

The accompanying drawings illustrate some constructions of incandescentcathodes according to the invention, as well as a discharge tubeprovided with an incandescent cathode constructed in accordance with theinvention. In the said drawings:

Figure 1 shows an incandescent cathode Gil 19,351, and in theNetherlands April 8, 1924.

with three parallel carriers, two of which serve to supply the current,the if-shaped filament portions being stretched at acute anglesrelatively to the carriers.

Figure 2 represents an incandescent cathode in which the filament ishelically wound on a number of metal supports.

Figure 8 is a cross-section taken on the line HIIII of Fig. 2.

Figure l shows an incandescent cathode in which the filament consists oftwo loops, the tops of which are directly connected to each other andhave wire wound around them.

Fig. 5 represents a discharge tube with three electrodes provided withan incandescent cathode of the same construction as shown in Figure 4.

In the incandescent cathode according to Figure 1 of the drawings metalcarriers and 62 serve at the same time as leading-in wires for V-shapedfilament portions 63. The tops of the wires (53 are connected to eachother by a carrier 61 which is secured by means of a wire to aninsulating tube 64 of quartz or similar material, which keeps thecarriers 60 and 62 spaced apart at the required mutual distance. Thewires 63 form acute angles with the'carriers so that the length of thewire between two, carriers is materially greator than the distancebetween the carriers, which offers the advantage that the resistance ofthe filament portions located between two carriers is greater than inthe case of a perpendicular arrangement.

The incandescent cathode according to Figures 2 and 3 of the drawingscomprises a filament 5, which is helically wound on four metal supports6, 7, 8 and 9. The filament may be secured to the supports for exampleby welding; the supports may also be pro vided with grooves, in whichcase the filament is inserted in these grooves and the teeth lyingbetween the said grooves, are preferably so bent as to lock up thefilament in the grooves.

The supports 8 and 9 are electrically connected to each other bytransverse pieces 10 and ll. and are arranged on a metal hood 12 whichis hermetically sealed to the. end of a glass tube 13.

The supports 6 and 7 serve for the'supply (leading-in wires 19 and 20being secured to the other side of the metal hoods. The glass tubes 13,17 and 18, are sealed to a glass tube 21. At the other end the supports6 and 7 are kept spaced apart at the required mutual distancev by a rod14 of insulating material,

for example, of quartz which rests on the transverse piece 10.

In this construction the helically wound filament consists in efiect ofa number of parallel connected filament portions, the supports 8 and 9which serve to support these portions, being connected to points havingthe same potential.

The incandescent cathode according to Figure 4 of the drawings comprisestwo loop shaped filament portions 32 and 33 arranged on U-shaped metalmembers 35 and 37 which are secured to supporting wires 36 and 38 whichalso serve as lead-in conductors. The tops of the loops 32 and 33 aredirectly connected to each other by a wire 34, for example, of tungstenwhich is. wound around said tops. This construction offers the advantagethat during the operation the tops of the filament have a lowertemperature than the other filament portions.

In the construction according to Figure 4 the two halves of each loopare connected in parallel to each other.

The discharge tube illustrated in Figure 5, may be used for example, asa transmission tube forwireless telegraphy. The envelope of thedischargetube consists of an insulating part 40'made, for example, ofglass and a metal part 41 sealed atits edge to the insulating part. Themetal vessel 41 acts at the same time as anode..

A re-entrant glass tube 59 is provided with glass tubes 42, 43 and 44the ends of which are hermetically closed by metal hoods 45, 46 and 47.A grid supporting structure is secured to the hood 46 and comprises asupport 48 and a metalplate 49 carried thereby.

0 this plate are secured four metal supports 50 on which the grid wire51 is helically wound. This wire may be connected to the supports'50,for example, in the same way as described with reference to theincandescent cathode'according to Figure 2.

Within the grid thus formed is arranged the incandescent cathode formedby two loops 57' and58, the tops of which are electrically connected toeach other and-which are secured to bent metal supports and 56. The

latter are carried by leading-in wires 53 and 54 which are secured tothe metal hoods 45 and 47. The discharge tube may be exhausted'in anyknown manner or may be provided with a suitable gaseous filling of lowpressure. The metal vessel 41 and the hoods 45, 46 and 47, mayadvantageously consist of chrome-iron of suitable composition.

What I claim is:

1. An incandescent cathode comprising a single coiled filament portionwound about a plurality of current conducting support members whereby aplurality of parallel current carrying paths are provided.

2. An incandescent cathode comprising a pair of conducting supportmembers insulatingly separated from each other and adapted to receivecurrent, a second pair of support members insulated from said firstnamed support members, and a single coiled filament wound about saidsupport members whereby current from one to the other of the firstmentioned pair of support members is caused to flow through the coiledfilament in a plurality of parallel paths.

3. An incandescent cathode structure comprising a pair of conductingsupport men1- bers insulatingly supported from each other and adapted tobe supplied with heating current, a second pair of support membersinsulated from said first named members, and a filament helically woundabout said first and second support members, whereby current from one tothe other of the first named pair of support members is caused to Howthrough the filament in a plurality of parallel paths, the second pairof support members being arranged to support the filament atequipotential points along its length.

In testimony whereof I afiix my signature, at the city of Eindhoven,this 19th day of February, A. D. 1925.

POPKO REINDER DIJKSTERHUIS.

